Include the iostreams standard header <streambuf> to define the template class basic_streambuf, which is basic to the operation of the iostreams classes. This header is typically included for you by another of the iostreams headers; you rarely need to include it directly.
For a list of all members of this header, see <streambuf> Members.
Reference
Thread Safety in the Standard C++ Library
iostream Programming
iostreams Conventions
Other Resources
<streambuf> Members
Standard C++ Library Header Files